1. Field of the Invention
The present invention relates to the technical field of source drivers and, more particularly, to a source driver with reduced number of latch devices.
2. Description of Related Art
FIG. 1 schematically illustrates the usage of a typical liquid crystal display (LCD) module, which includes an application processor 110, an LCD module 120, and an LCD screen 130. The application processor 110 receives an image signal from a storage device (not shown), and a clock controller 121 of the module 120 sends the image signal to a plurality of source drivers 123 through a data bus 127. The source drivers 123 of the module 120 latch the data and, in cooperation with a plurality of gate drivers 125, drive the LCD screen 130 to play the image signal on the LCD screen 130.
FIG. 2 is a diagram of a typical source driver 123 configuration. First, a first-stage latch 210 is controlled by a latch enable signal S and a complementary latch enable signal SB to fetch and buffer digital data D1-D6 on the data bus 127. Next, the digital data D1-D6 on the data bus 127 is sent to a second-stage latch 220, a level shifter 230, and a digital to analog converter (DAC) 240 for being converted into an analog voltage to output.
FIG. 3 is a circuit diagram of a typical latch circuit. When the latch enable signal S is at a high voltage VPP and the complementary latch enable signal SB is at a low voltage VGG, the latch 210 or 220 is in a sample mode, and transistors MPT, MNT allow the voltage on the input D to pass. When the latch enable signal S is at the low voltage VGG and the complementary latch enable signal SB is at the high voltage VPP, the latch 210 or 220 is in a hold mode, and the transistors MPT and MNT are closed so as to prevent the voltage on the input D from passing through he circuit, while the transistors MPHZ and MNHZ are turned on to latch the voltage passed in the sample mode. However, the required number of the source drivers 125 rapidly increase as the resolution of the LCD screen raises.
Therefore, it is desirable to provide an improved source driver device to mitigate and/or obviate the aforementioned problems.